Electrical heating



Oct. 29, 1929. l A H DAVlS, JR 1,733,250

ELECTRI CAL HEATING Filed Nov. 5, 1925 Patented `Cot. 29,5 19.29

UNITED STATES PATENT ori-lice AneHIBALD H. DAVIS, JR., or BUFFALO, NEW Yonx, AssIGNoR 'ro NATIouAL ANrLmE AND cHEmIoALco., INC., or NEW'YoRx, N. Y., A coRronA'rIoN- oF NEW Yom:

ELECTRICAL HEATING Application tiled November 6, 1925. Serial No. 67,296.

This invention relates to electrical heating and in particular to electrical heating of pipe lines connecting electrically unins'ulated apparatus.

For conveyingsubstances that tend to solidify at ordinary temperatures,'it is-necessary that the pipe line conveying such material be heated to maintain a fluidV condition.

The usual method of employing gas burners ing, and is distinctly hazardous.Y Accordingly heatigg with electric current is desirable; but, as a pipe line, when connected to apparatus, cannot be readily insulated, usually other vpaths for the iiw of .current exist in additionto the pipe line in parallel conductive relationship therewith. The result is that current follows the other paths, and these stray currents may be large compared with the eiective current through the .pipe line. Current 'is consequently wasted `in heat,

where itis not needed or wanted.

It is anobject of my invention to provide electrical heating means for a pipe line or a similar body having electrically uninsulated connections. Another object is the heating of a pipe line or a body by electric current where stray paths for currentexist b v causing a iow of current in the pipeline or body while substantiallv avo'ding the 'flow-of current in the stray-paths.

These an other obiects I accomplish by connecting the ends ofthe pipe line to one terminal of a source of current, and the other terminal of the current source to a point or points intermediate the ends. The current is thus divided into branches through the pipe line'. and there can be no appreciable flow of current through' other paths between the pipe ends, since there is no material difference of potentialto cause the iow.

In the drawing, Fig..1 diagrammatically illustrates a pipe line associating two pieces of `apparatus and a circuit including thelpipe line.

Fig. 2 is a diagrammatic illustration of a pipe line connecting a plurality of pieces of apparatus and the heating circuit. -Y K In Fig-1,41 pipe line -1 connects a blow case 2. and a vfusion pot 3. As these'structures are carried on the frame of the building which,as

arule,'consists of steel members 4, it 1s evident that a path for electric current from the pipe exists through the structures and the building as well as through the pipe. Such stray currents are avoided by connecting both ends of the pipe line 1 to one terminal of the transformer 5 by two conductors or leads 7.

connected through a lead 6to a point midway of the pipe ends. 'With a midway connection of the lead 6, the pipe is substantially uniformly hea/ted throughout itslength; but the -lead 6 may be connected at any point interends a, b, 0,' and leads 17 and 18 extend fromv the ther terminal of the Jtransformer to intermediate points e, f vof thepipe line. As' -suming that the leads to the pipe line'have negligible resistance and the pipe line has, for example, the resistances thereon indicated in the figure, it is not feasible to connect one terminal from the source to the pi re ends, a, b, 0,

l, The othergterminal of the transformer 5 is involves uneven heating'and risk of overheatandthe other to the midpoin d, because the current flow through the section d, b, having.

one third of the resistance, will bethree times J n n as great. To overcome thls, when uniform heating is required, the second terminal is connected to points, such as e and f, which delimit sections of the pipe line extending from the pieces of apparatus .into units', of substantially equal resistance. However,

ywhere the connection of a section extending from a piece of apparatus to the pipe line, as point, d, is intermediate such'points, two returns in parallel existfrom such a point d to the adjacent terminal connections, e and f, and the current isconsequently dividedv betweenthem. To correctl this condition, the point d is connected by a lead 194 to a tap 20, so located onthe source that a potential is applied across each return sutcient to 'secure a full current liow..

t With additional piecesof apparatus, connections are made, as illustrated and explained with regard to Fig. 2. yIt can thus be extended, to heat with substantial unit'ormity, pipe lines connecting any desired number of pieces of apparatus that arel grounded without perceptible leakage.

The system disclosed is susceptible of various modifications. Taps on the source whereby the voltage is divided to give the desired RI drop in any section of the pipe lines can be used, and points of like potential can be associated by common leads.

While the invention is disclosed in its application to pipe lines, it is evident that it has other uses and is not to be restricted thereto.

,I claim: l l. A method of electrically heating a plurality of interconnected sections which comprises maintaining substantially equal potential on the ends of said sections, imposing a different potential at points of substantially equal resistance measured from such ends,

' and applying proportionate potential at intermediate points delining sections connected in parallel to cause a substantially uniform` current within all of the sections.v A

'2. A system for electrically heating a. body having a pathcapable of conducting current in parallelconductive relationship therewith comprisinga source of current, leads from one terminal of said source to the ends of the body,and a vlead from the other terminal of said'source to a point intermediate the ends of the body. i

3., A system for electrically heating a pipe i line having sections connected to a plurality of pieces pable of conduct-ing current in parallel conductive relationship therewith, said system comprising a. source of current, leads from one terminal of said source to section ends attached to the ap aratus, and leads from the other terminal o `said source to points in the rpipe line intermediate the sections.

` 4. A system for electrically hfgting'a pipe line having sections connected to a plurality of pieces of apparatus, said system comprising a source of current, leads from one terriginal dhs it the apparatus,'leads from the other terminal of said source to points in the pipe linefdelimiting sections having substantially v. the

'same resistance, and leads tapped from said source to interconnections defining sections'rof lbody at substantially equal aid source to section ends attached of said source to points in the pipe line delimiting sections having substantially the same resistance, and leads tapped from said source to portions of the pipe line connected in parallel for applying potential to said portions to cause a uniform current flow.

6. A method of electrically heating a body having a path Vcapable oi conducting current in parallel conductive relationship therewith which comprises maintaining the ends-of the potential'and imposing a diiferent potential intermediate the ends to cause a iow of current in said body While substantially avoiding the flow of current through said path.

7. A method of electrically heating a body of substantially uniform linear resistance having a path capable of conducting current in parallel conductive relationship therewith which comprises applying substantially equal potential at the ends and a different potentialmidway of the ends of said body to cause a flow of current in said body while substantially avoiding the flow of current through said path. 8. A method of electrically heating a plurality of bodies having an end ot each connected with the other bodies and having a path capable of conducting current in parall`el conductive relationship therewith which comprises maintaining substantially equal potential on the unconnected ends of said bodies and imposing a different potential at a Vpoint intermediate the unconnected ends of said bodies to cause a How of current in said bodies while substantially avoiding the flow of current through said path.

In testimony whereof I aix Davis, JR.

of 'apparatus and having paths cadiierentconductivity for applying proportionate potentials. i

5. A System for electrically heating a pipe line havlng sectionsconnected to a plurality said systelncomprisof pieces of apparatus,

leads from one termithe apparatus, leads from the other terminal 

